1. Field of the Invention
The present invention relates to an image forming apparatus and a sheet processing apparatus which are provided with a bookbinding mode for forming images on sheets and bundling and bookbinding the sheets having the respective images formed thereon, and a method of controlling the sheet processing apparatus.
2. Description of the Related Art
Conventionally, as a post-processing unit of an image forming apparatus, there has been proposed a glue binding device which glues one side of a sheet bundle comprised of a plurality of sheets, encases the sheet bundle in a cover sheet, and selectively trims the other sides of the sheet bundle (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2005-104063).
In the conventional glue binding device, in the case where a job of the image forming apparatus is stopped in the middle of execution thereof e.g. in response to job cancellation by depression of a stop key of the image forming apparatus, sheets having respective images formed thereon are sequentially discharged from the image forming apparatus until the job is actually stopped. The discharged sheets are sequentially stacked into a bundle within the glue binding device. This sheet bundle does not contain all pages of the job, or in other words, the sheet bundle is an unfinished article, so that the user has to remove the sheet bundle from the glue binding device.
However, the stacked sheet bundle is sandwiched with a predetermined pressure, and hence a large force is required for the user to remove the sheet bundle from the apparatus, which can make it difficult to carry out the removal. Further, the side alignment of sheets of the sheet bundle can be inconveniently lost during the removal operation, which can cost the user time and labor.